1. Field of the Invention
This invention relates generally to a device for holding down a buried pipeline, and more particularly, but not by way of limitation, to a slot form for pipeline buoyancy control.
2. Description of the Related Art
Large diameter pipelines over thirty inches in diameter will float in water with only 40% submerged. In high-density soupy soils, the pipe will float with only 20% submerged. The art of keeping a pipeline buried in these conditions is called buoyancy control.
Current methods of buoyancy control are concrete set on weights and gravel filled bags. These are density-type buoyancy control and work by adding weight to the pipe. There are several more methods available but they have not been accepted by the pipeline industry because of cost.
Set on weights, as shown in FIG. 1, are weights made of concrete with an inverted-U-shaped cross section to allow the weight to be placed over the pipe. The weight will hold the pipeline in place. Bags filled with gravel may also be used, as shown in FIG. 2, with one bag located on each side of the pipe and a flexible strap over the pipe attaching the two bags.
The problem with both of these prior art devices for buoyancy control is that they are heavy and must be constructed off site and transported to the pipeline, where they must be placed on top of the pipeline at regular intervals. This requires considerable installation costs, including the costs of transportation, machinery, and manpower, given the extreme weight of the devices and their bulky nature.
Based on the foregoing, it is desirable to provide a device for buoyancy control that is lightweight and capable of being installed without the use of lifting equipment.
It is further desirable to provide such a device that requires minimum labor for installation.
It is further desirable to provide such a device that reduces the cost of installation compared to set-on weights or bags, thus reducing the cost of service for transporting product through the pipeline.